From 4a5c16d06593981e48e760f76f09f3fecaf14a1a Mon Sep 17 00:00:00 2001
From: David Howells <dhowells@redhat.com>
Date: Thu, 4 Apr 2024 16:05:19 +0100
Subject: [PATCH] cifs: Fix reacquisition of volume cookie on still-live
connection
[ Upstream commit dad80c6bff770d25f67ec25fe011730e4a463008 ]
During mount, cifs_mount_get_tcon() gets a tcon resource connection record
and then attaches an fscache volume cookie to it. However, it does this
irrespective of whether or not the tcon returned from cifs_get_tcon() is a
new record or one that's already in use. This leads to a warning about a
volume cookie collision and a leaked volume cookie because tcon->fscache
gets reset.
Fix this be adding a mutex and a "we've already tried this" flag and only
doing it once for the lifetime of the tcon.
[!] Note: Looking at cifs_mount_get_tcon(), a more general solution may
actually be required. Reacquiring the volume cookie isn't the only thing
that function does: it also partially reinitialises the tcon record without
any locking - which may cause live filesystem ops already using the tcon
through a previous mount to malfunction.
This can be reproduced simply by something like:
mount //example.com/test /xfstest.test -o user=shares,pass=xxx,fsc
mount //example.com/test /mnt -o user=shares,pass=xxx,fsc
Fixes: 70431bfd825d ("cifs: Support fscache indexing rewrite")
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
cc: Shyam Prasad N <sprasad@microsoft.com>
cc: linux-cifs@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/client/cifsglob.h | 2 ++
fs/smb/client/fscache.c | 13 +++++++++++++
fs/smb/client/misc.c | 3 +++
3 files changed, 18 insertions(+)
diff --git a/fs/smb/client/cifsglob.h b/fs/smb/client/cifsglob.h
index 68fd61a56408..12a48e1d80c3 100644
--- a/fs/smb/client/cifsglob.h
+++ b/fs/smb/client/cifsglob.h
@@ -1247,7 +1247,9 @@ struct cifs_tcon {
__u32 max_cached_dirs;
#ifdef CONFIG_CIFS_FSCACHE
u64 resource_id; /* server resource id */
+ bool fscache_acquired; /* T if we've tried acquiring a cookie */
struct fscache_volume *fscache; /* cookie for share */
+ struct mutex fscache_lock; /* Prevent regetting a cookie */
#endif
struct list_head pending_opens; /* list of incomplete opens */
struct cached_fids *cfids;
diff --git a/fs/smb/client/fscache.c b/fs/smb/client/fscache.c
index a4ee801b2939..ecabc4b40053 100644
--- a/fs/smb/client/fscache.c
+++ b/fs/smb/client/fscache.c
@@ -43,12 +43,23 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon)
char *key;
int ret = -ENOMEM;
+ if (tcon->fscache_acquired)
+ return 0;
+
+ mutex_lock(&tcon->fscache_lock);
+ if (tcon->fscache_acquired) {
+ mutex_unlock(&tcon->fscache_lock);
+ return 0;
+ }
+ tcon->fscache_acquired = true;
+
tcon->fscache = NULL;
switch (sa->sa_family) {
case AF_INET:
case AF_INET6:
break;
default:
+ mutex_unlock(&tcon->fscache_lock);
cifs_dbg(VFS, "Unknown network family '%d'\n", sa->sa_family);
return -EINVAL;
}
@@ -57,6 +68,7 @@ int cifs_fscache_get_super_cookie(struct cifs_tcon *tcon)
sharename = extract_sharename(tcon->tree_name);
if (IS_ERR(sharename)) {
+ mutex_unlock(&tcon->fscache_lock);
cifs_dbg(FYI, "%s: couldn't extract sharename\n", __func__);
return PTR_ERR(sharename);
}
@@ -90,6 +102,7 @@ out_2:
kfree(key);
out:
kfree(sharename);
+ mutex_unlock(&tcon->fscache_lock);
return ret;
}
diff --git a/fs/smb/client/misc.c b/fs/smb/client/misc.c
index 74627d647818..0d13db80e67c 100644
--- a/fs/smb/client/misc.c
+++ b/fs/smb/client/misc.c
@@ -141,6 +141,9 @@ tcon_info_alloc(bool dir_leases_enabled)
atomic_set(&ret_buf->num_local_opens, 0);
atomic_set(&ret_buf->num_remote_opens, 0);
ret_buf->stats_from_time = ktime_get_real_seconds();
+#ifdef CONFIG_CIFS_FSCACHE
+ mutex_init(&ret_buf->fscache_lock);
+#endif
return ret_buf;
}